FIGURE 3.

PKD1-ΔPH is a constitutively phosphorylated enzyme that displays a high level of CREBtide and CREB kinase activity. WT-PKD1 and PKD1-ΔPH immunoprecipitated from HEK293 cells were used in IVKAs without or with PMA or DS (with CREB as substrate) as described under “Experimental Procedures.” Left, autoradiography and immunoblotting for PKD1 activation loop and Ser⁹¹⁶ phosphorylation. Right, ³²P incorporation into PKD1 (top) or CREB (bottom) was quantified by PhosphorImager. The data are from a single experiment, with identical results obtained in two separate experiments.